Remote validation of combo on select does not make any sense as if some of the values in the list is invalid why it is there in the first place.

It does make sense for user typed values in combo and in that case keyup triggers remote validation.

It does make sense if you want to build a secure form (hence the reason I chose for remote validation). The project I'm working at requires a very high level of security, and by validating the fields remotely I keep all field requirements away from 'those eyes'.

Yes, I populate my como with values/text loaded at init, but since the source can easily be tampered with I validate ALL fields remotely, so also the combo boxes. This way I can assure the form is completely valid at submission...